They are not quite on the same scale as losing Venus Williams, who pulled out of this year's ASB Classic, but the Heineken Open has been hit by the withdrawal of three well-known players for next week's event.

Juan Monaco, Tommy Robredo and Fernando Gonzalez have all pulled out of the tournament because of injury and illness and will be replaced by Rui Machado (ranked 68) of Portugal, Italian Filippo Volandri (69) and Lukas Rosol (70) of the Czech Republic.

Monaco, at 26 in the world, was the tournament's fourth seed, but doesn't want to risk aggravating the wrist he injured in the Davis Cup final against Spain with the year's first grand slam around the corner.

Gonzalez (virus) has played little in the past 12 months and was playing with an injury-protected ranking of 55. He and Robredo (leg) have also pulled out of the Australian Open.

All three have been regulars in Auckland and Gonzalez won in 2005. Robredo was runner-up in 2007, losing to this year's top seed David Ferrer, and picked up the doubles title last year. This would have been Monaco's seventh appearance at the Heineken Open.

"You don't want to lose players of that quality,'' Heineken Open tournament director Richard Palmer said. "You could argue Gonzalez hasn't played in a while but Monaco had a good end to the year and it's unfortunate he's withdrawn.

"Robredo is an old warhorse who's dropped to 54 but always gives his best so it's not good to lose someone like that. But these [new] guys, who knows? They didn't expect to get in and they are going to be pretty hungry for it. There could be an upside to that.''

Palmer is hopeful no more players pull out, particularly the Spanish trio of Ferrer (5), Nicolas Almagro (10) and Fernando Verdasco (24) who will be the top three seeds.

American Sam Querrey, who last January was ranked 17 in the world but who has slipped to 93 after three months sidelined following elbow surgery, picked up the last of the three wildcards for the tournament. Fellow American Ryan Harrison and Kiwi No 1 Michael Venus gained the other two.